Method osi investigating minute movements and distobtion in structuees



Sept. 8, 1925. I 1,552,452

H. F. ROACH 7 METHOD OF INVESTIGATING MINUTE MOVEMENTS AND DISTOK'TION IN STRUCTURES Original Filed April 29', 1922 Patented Sept. 3, 1925.

earner tries.

HARRY 30.51.0531, 03? ST. LOUIS, MISSOURI.

original n ti filed April 29, 1922, Seria1 No. 557,320. Divided and this application. filed August 2, 7

Serial N'o. 728,739.

T all whom it may concern:

Be it known that I, HARRY F. loner-r, a citizen of the United States, residing in the city of St. Louis and State of Missouri,

have invented new and useful Improvements in Methods of Investigating Minute Movements and Distortion in Structures, of which the following is a specification.

This application is a division of application, Serial No. 557,320, filed April 29th, 1922.

The invention relates to a method for observing or investigating minute movements which may occur in a body for any reason, and while the invention may be applied in any situation where a minute movement is to be observed, it is especially useful in observing or investigating the minute movements which occur in an engineer ng structure when the same 1S sub ected to a load. By observing and determining the movements or distortion of any structure or member subjected to a load, much information may be deduced as to the fibre stresses which have been developed. The general object of the invention is to provide a simple method to enable such very minute movements to be rendered plainly visible, at the same time avoiding errors of chromatic magnification and aberrations in-si dent to dioptric optical system in great nragnifications in one direction; also to make prominent the indicated movements in a direction parallel to an axis of selec tion. All the errors of a dioptric system may be eliminated if in any case found .desirable by the use of a catoptric optical sys tem in connection with my magnifying elements. As applied to the observation of distortions or movements of a member under a load, one of my objects is to provide a simple method for graphically indicating, and also for recording distortions which occur by reason of the load. As one example of the use of my method, I have de scribed it as employed to indicate to the eye the movements in a track rail which may occur on account of a load passing over the rail, and when my method is applied in such a case, it not only enables vertical movements and vertical distortions of the rail to be observed, but also enables the determination of simultaneous movements which occur in the rail in a longitudinal direction, and which give information useful in the solution of problems relating to rail creeping and ballast. reaction.

Another example is the observing .or recording of strains of amember, from which stresses may be deduced.

The information conveyed 'by such investigations is very useful in studying the engineering problems incidental to railway construction.

In practicing my method I may, if desired, produce simultaneously two images or two photographs of the object, one of which indicates to the ey the minute movements of the object withrespect to one axis and the other indicates minute movements with respect to another axis.

Further objects of the invention will appear hereinafter. v

The invention consists in the novel features, and in the general combination of steps to be particularly described hereinafter, all of which contribute to produce a simple and etficient method of investigating minute movements, and distortion in structures. A preferred embodimentof my invention will be particularly described in the following specification, while the broad scope of my invention will be pointed out in the appended claims.

In the drawing' Figure 1 is a diagrammatic plan, illustrating the apparatus which I employ in using my method to determine movements in arail on a railway track;

Figure 2 is a plan diagrammatically illustrating a camera partially broken away and shown in section, and further illustrating my method;

Figure 3 is arhorizont'al section through the camera attachment which I may employ to facilitate the practice of my method;

Figure 4 is a diagrammatic plan showing a camera partially broken away and shown in section, in order to illustrate oneof the steps which may be employed in my method;

Figure 5 is a side elevation upon an enlarged scale showing a short portion of a rail and illustrating one of the steps which I may employin practicing mymethod;

Figure 6 is an end elevation of the rail shown in Figure 5;

Figure 7 is a diagrammatic view indicating the character of an anamorphous photograph which indicates the vertical rail distortions which occur under the act-ionbf the load upon the rail;

F ignre8-is a-v-iew illustrating the char acter of a transparent screenwhichI may employ in assisting to determine the longitudinal movements which occur in the rail, simultaneously with the vertical distortions indicated in Figure 7 and" Figure 9 is a' diagrammatic view illustrat ing the character of ananamorphous photo graph which indicates the amount ofmovement of a certain point on therai'l,.which occurssimultaneously with the vertical ira'il distortion'indicated in Figure 7.

In practicingthe various iarts it is often necessary to investigate minute movements whichv may occur, .due to .physicah che'mi cal or other forces. In physical laboratories it is, of course, possible to employ high-' poweredmicroscopes "through the agency of which mmute movements maybe observed, but such IDICIOSCOPGSlTlLlStBHlbOClY n their constructionvery carefully" ground ztndexpensive lenses which-must have correction fol-aberration, astigmatism and other clefects which areinherent in lenses, and they arelimited to' mag-nification in all directions, which, in very high magnifi'cation,' renders impracticable the imposition of scale into the image.

Vhile. my method may be employed under any: circumstances to T observe minute move-x 'ments'iofany kind, 1t 1s-part1cularly useful as applied to the solution 1 of 5 engineering; problems through the investigation-of i the' movements which occur-in-astructurefwhen,

the load i's applie'd to it: Fonexample; thevibratory movements" occurring in bridges can be investigated, or any movementsi'oocurring in columns, girders on any other members :of an engineering structure.

Inzlth'ea following specification, by-way of example, :I. have described'the method as applied to the observation orinvestigati'ono-f'movements occurring in a rail on a railway track, when-yit is subjecte-d t o a loa'd-." When applied .to: such a purpose my method I enables the vertical or perpendicular dis--- tortions of; therrail to bedetermined with accuracy, and, if desired, the simultaneous movement :of a predetermli'ied l point I on the rail may 'bedetermined;v th'ereby, "giving data which is usefulvin solvinggprob lemsof Lrail creeping; and ballast reaction In Figure '1, Iirepresents a rail on a piece-" of'track which is to be investigatedzi' Op posite this r rail :1; set ups: tripod; the; head 2: of, which ofi ersrarsupport for: cameras;

preferably-s three in number, zandgdesignated i by the-letters ;A,.;B1iand 6.. Theseecameras only, parallel with a given 'aXis.

present instance this. axis along wh ch magnification occurs in the camera B, is a "ertical axis and, hence the image and photograph formed by this camera'possesses a relative magnification in a vertical direction, only. The camera C, is provided with my attachment, but the attachment is so placed that an anamorphous image and" photograph may be formed in which high magnification occurs parallel with another 5 axis; in the present instance this axis 182,

substantially horizontal line; that. is tosay, the line along which the rail extends.

While in the present instance it; will benoted thatthe two axes referred to are at right angles to each other, it should beunderstood that this is merely ineident-al and that the direction of magnification in the two images-or photographs formed may have any angle with-respect tozeach other that may be desired. In other words, this step. of my method involves'themalring of two difierent-anamorphous. images simultaneously, each image having magnification on a certain axis diiferentfromthe direction or axis .of magnificationrin the other image. or photograph- In consideringthis subject it should be evident that a track rail even on a nearly perfect piece of track does not have its upper face disposed in a plane, in other words,:as viewed. in side elevation, no rail on a track is strai ht, hence if an image or photograph were made of it, in' order toindicate how therail has been distorted; by the load upon it, such an image or photographwould not represent the net distortion which occurredrin the rail .due to the load. This difficulty .might not arise in some: structures, which. would naturally;

present upon them a substantially straight line which, when an image 1s. made, would be shown in the photograph as. distorted. from the straight position. In the present instance, however, I overcome this dificulty byplaci'ng on the side of the rail head, a straight line 3 (see Figure 5.) which may he' -made, if desired, by means ofa chalked line, orinany other mannerrwhich will insure a substantially straight line being Having formed this-line inthisgwayyI place-the load,for-example,.a. locomotive; on -t-he-rai'l at the point being investigated. The camera B, which produces vertical magnification only, will then produce an image of the line 3 in which the upper edge of the chalk line will be indicated as bent into a curved or sinuous form, such as that indicated by the line 4 on the plate 4 (see Figure 7 This magnification is effected by the use of lenses to be fully corrected to and including the actinic rays, and by means of a series of reflectors that divert the rays as they pass into the camera, the reflections occurring on curved reflectors in such a way that magnification occurs only parallel with a given axis; in this way, in the camera B, magnification occurs in all vertical dimensions, but the horizontal dimensions on the image or photograph are normal, that is, the same as would occur in a normal photograph or image formed with the same lenses, placed in the same way.

My attachment E, by means of which I effect this anamorphous result in the image, is illustrated in Figure 3 and comprises an object lens 5, fully corrected to and including the actinic rays, at the forward end of the attachment through which the rays pass am the camera. From this lens the rays pass thr ugh a suitable stop 6 and are reflected upon a curved reflector preferably a convex reflector 7, of cylindrical or elliptical form, the axis of curvature of the reflector being disposed in a horizontal position. From the reflector 7, the light raysare inclincd up or down in a vertical plane and fall upon a reflector 8, which may be a plane reflector, if desired. From this point the rays pass over to another curved reflector 9, whica is similar to the reflector 7 and from which they pass up on to a re tlector 10, which may be a plane reflector. From this point they pass through a second lens 11, corrected similar to lens 5, and into the camera box where they produce an anamorphous image upon the plate or screen held therein. It will be understood that the relative angular positions of the curved reflectors is such as to produce a balanced distortion of an image according to the principle fully explained in my pending application Serial Number 537,436, filed February 18th, 1922.

in the camera C, which produces an anamorphous image magnified in the horizontal direction, the attachment shown in Figure 3 is employed, butit is held in a position in which the axes of curvature of the reflectors 7 and 9 are in a vertical position. The attachment operates in the same way upon the rays of light, except that the magnification is produced in a horizontal plane instead of in avertical plane as in the camera B.

The camera B enables minute movements which occur in a vertical direction in the rail or any other body, to be observed, for itwill be evident that if this camera is held fixed, it will produce an anamorphous image on the screen or ground glass plate 12, in which the magnification occurs solely in the direction in which the transverse movements of the rail take place; this magnification will be sufficient to render the movements sensible to the eye; by observing the image on the ground glass 12 before the load has been put upon the rail and again after the load has been put upon the rail, the movements of the line, such as the line 4 (Figure 7) will be observed, and the amount of movement can be noted.

In order to enable the camera G to pro duce an imageonits ground glass plate 13, which will indicate the amount of movement of a predetermined point of the rail, I pres for to provide on the rail a short vertical line or mark 14 (see Figure 5) -Wl1lCl1'6X- tends at right angles to the line 3. Within the camera C I place a transparent screen 15, in front of the ground glass 13, and this screenis provided with a line or indicated mark 16, which passes vertically across it. An image of the point 14 will then appear on the ground glass screen 13; the camera box 6 should then, before the load is placed on the rail, be adjusted until the image of the point 14 coincides with the line 16. The locomotive or other load should then be placed upon the rail and when this occurs a shifting movement will occur of the point 14, i and due tothe magnification which occurs in the horizontal dimensions of the image, the image 17 of this point; will be found to be moved slightly out of alignment with the mark 16. In this way the relative amount of movement of the point 14, incidental to a given rail distortion indicated on the ground glass 12, can be observed, and furthermore, if desired, these tWo images may be concurrently observed by placing the cameras close together, as shown.

The image on the screen 12, as intimated, will have-the character of the sinuous line 4 shown in Figure 7, and the char acter of this line will be of interest to the engineer or other observer, in investigating the distortion in the rail which a given load produces in a given position.

If it is desired to make a permanent record of the images formed in the cameras, it is simply necessary to place a sensitized plate in each camera in the proper position, and expose the same in the usual manner in taking photographs. It is necessary, however, to have in the finished photograph, some means for determining what the normal scale of the photograph is with respect to the-rail. For this purpose it is merely necessary to photograph a two foot rule in the field of the camera and extending at right angles to the direction in which maglll) nificationnistooccur; or I may place two: marks: :18rand 19 on the: side of thevrail, at a predetermineddistance: apart.

llprefer to ascertain this normal scale by 1 photographing the rule or other scale'on a photographic plate exposed" in the camera A, :at the sametime that the exposure of the sensitizedlplate is madein'the camera B. The cameras are all atthe same-distance frdnrthe 'railand'arranged so'that'the' images are alike and 'on-the same'scale-except for-thes distortions in-one direction. Hence,

a sensitized plate 20 exposed in the camera:

'Aiwill give what-"Icall the normal scale for the photographs.

I11 Figure 7" the "portion of the "plate below the: line 1 4* represents a magnified area 'ofthe line =3, a while the space above it will show a small portion'ofi the side of the rail head "aboverthisdine; The actual distortion and relativefibrestressesare indicated by the character of the bends ain'this line 4F, and by reason of. Itheifact that we know the amount of magnification, and also the normal scale otthis photograph, we areenarbledto compute by engineeringfformulee applied to: this curve, the fi'bre 'stresswhich must have occurred inf-the rail to correspond with the ac- 1 tual distortion indicated by v the photograph. If: desired; .Imay produce a' photograph similar: to that shown in F igure 7 by pro ducing an anamorphous reproduction or" photograph of the plate 20 of thecamera A,

after the same has been developed, the' 'magnification'i in the new photograph: occurring in a vertical direction. Figure lillustrates how this could be accomplished, by placing the photograph before a camera D, which is similar inconstruction .to the cameras B and G. Howeverg'in'Figurea the attachment E is'illustrated in thetposition' to produce magnification in a horizontal direction, only, and with the attachment in this position, I em-v ploy this camera D, if desired; to produce a "photograph! from the sensitized plate 13,

after development: By doing so-,' .a magnification occurs in a: horizontal :direction; and the result is a photograph or plate21 such as indicated in- Figure '9, inwhich the vertical band 22irepresentsthe line 16 aszit would bemagnifi'ed, and the'area 23 indicates the point or mark 14 magnified; :the' distance between the band. 22 and the area 23, in'dicatesorirecords permanently the amount of "movement whichoccurs atthe point l l on the rail. The camera' D in this position maybeiused: on the: plate SllOWII-l in Figure 7, by turning the plateithrough90' degrees before photographingiit,or, if?desired, the platemay be left "in? an cuprightposition, and? the." attachment E rotated on :its: longitudinal axis. c In practi'ce,= when great accuracy: in the deductions i's desired; Irpreferrto produce the:

anamorphous plates byuse of the cameras B ments of the normal photograph=tak'en with the-camera ;A. v The two resultsoperate as: a check upon eachotheriandtheir conf'ormity' will be a criterionof theaccuracy of the-ob servations; More reliance may be placed on the use of the' photographic plate 20of-the camera A, where the light conditions: are .not suchas to produce the best' results: with cameraB: v

I- have referred :to" the-transversemove-;= ments' ofrthe rail as vertical movements, in;' stead of lateral movements: because "the word l'ateral used in connection with a track would mean: horizontal; But it is understood that my method'renders' it possible to investigate any movements Y or distortionswhich 'occur'in' a plane transverse to the lon-i gitudinal-axis of the body.-

In practice a relative'magnification at -the ratioo-t tOO to '1'ca-n 'be readily obtained in the anamorphous images or photographs,- which will be found I ample for ordinary pra-ctioeybut in case ofspecial investigation this 1 relative magnification may: be stepped up by repeated photographing as illustratedin Figure 4;, to any degree desired.

I claim:

1. The method of investigating distortion in a'loadedstructure which consistswin produc'inga normal photograph of the structure while subjected-to the load and'then produc-- ing a balanced anamorphous photograph of the" image of thenormal photograph in which magnificationf'occurs only. in the direction in which the' distortion occurs in the structure.

' 2. The methodof investigating themove mentoccurring in a longitudinal direction in an elongated member subjected to a load, which consists/in placing an indicating mark on the side of the member, producingan an.- amorphous image i of the memberupon a screen-having a marked point registeringy v with the-image of the-marked point on the memben'while the member is at rest, placing a sensitized plate back ofthescreen" at the position ofutheimage, subjecting. the mem- "the plate? In 'testimonywvhereofil have hereunto set my hand I HARRY r. noacn; 

